1. Field of the Invention
The present invention relates, in general, to a method of detecting false or counterfeit data recording media and a data recording medium therefor. More particularly, the method and medium of the present invention is of especial utility in detecting unauthorized copies of magnetic cards adapted to encode credit data, identification or other information and is used to elicit service from one of a plurality of automatic service rendering or product vending machines. Such machines are typically set up in a service area for the dispensing of a product or a service in response to the presentation of the data recording medium to one of such machines. The value of the service rendered or the product dispensed by the automatic machine is subtracted from the users credit and any remaining credit is re-encoded on the data recording medium.
2. Description of the Prior Art
Theoretically, any number of magnetic credit cards or other data recording media may be forged, for example, by simply copying the information encoded on such checking or credit cards. These copied, or false, cards may then be used in several automatic service machines at a time at which indirect transmission and dissemination of counterfeiting information as provided for in the present invention is not prevented by otherwise attended operation. Such attended operation, while theoretically possible, is nonetheless inconsistent with the basic of concept of setting up automatic service machines in the first place. Such a scenario, while an extraordinary one, may nonetheless be remedied by various measures. For example, provisions may be made for a privilege system which provides for an allowed service area to be activated at given time intervals, which may be effected in the following manner: A privilege code is issued at a central location with the aid of random numbers. Each data recording medium, such as a checking or credit card, must initially be presented at that central location for verification and automatic encoding with a privilege code, which code is valid for only a specific period of time. All automatic service machines in the allowed area must then be set up to accept only those data recording media which have been properly privilege encoded. In a system of this kind, a false medium will be reliably recognized at the central location and may then and there be withheld to prevent futher abuse. Such a technique is, of course, more complex and functionally undesirable.